Intertitial cnidarians: Halammohydra sp. and Pinushydra chiquitita

The video shows two cnidarians representative of the class Hydrozoa that spend their whole life in the interstices of sand grains: Halammohydra and Pinushydra chiquitita. These two tiny species are morphologically quite different from each other. But both are predators and use stinging cells (cnidae) to catch prey. Both have flexible and slender bodies that allow them to move through the narrow spaces of the sediment. And both can firmly adhere to sediment particles using special adhesive structures, so the